The letter, authored by committee chairman Trey Gowdy, makes the astonishing claim that "nearly half of all emails sent to and from Secretary Clinton regarding Benghazi and Libya prior to the Benghazi terrorist attacks involved Sindey Blumenthal." Those email include several message sent in July 2011 in which Blumenthal mentioned the firm Osprey Global Solutions, which was seeking private security contracts from Libyan forces opposed to Muammar Gaddafi. Blumenthal has acknowledged having a personal financial stake in the firm.

Blumenthal warned Clinton that French companies had visited Libya in an effort to secure security contracts, and suggested it would be in America's interest if Osprey won the contracts. Emails show that Clinton promoted the idea of using private security firms to protect Libyan revolutionary leaders, and told State Department aide Jake Sullivan that "the idea of using private security experts to arm the opposition should be considered."

Even more worrying is the evidence suggesting that an email correspondence between Clinton and Blumenthal included the name of a CIA "human source" that should have been considered highly classified information and should not have been transmitted via an unsecured private email server. Blumenthal received the information from Tyler Drumheller, a former CIA official who also had a financial stake in Osprey Global Solutions. Yahoo Newsreported on the seriousness of the allegation:

[W]hile there is nothing that indicates that the email from Blumenthal (who was not a government employee) was marked classified at the time Clinton received it, the sensitive nature of its contents should have been a red flag and never should have been passed along, according to a former veteran CIA officer.

"She is exposing the name of a guy who has a clandestine relationship with the CIA on her private, unprotected server," said John Maguire, who served for years as one of the CIA’s top Mideast officers.

In addition, he noted, the email should trigger a "crimes report" by the CIA to the Justice Department seeking an investigation into who within the agency revealed the information to Drumheller.

John Rizzo, a former CIA general counsel, told Yahoo the identity of a human source is "the most sensitive kind of classified information." Clinton "should have told Blumenthal, ‘delete this — and don’t send me that again.’ And then she should have reported it to State Department security," Rizzo said.

Clinton campaign spokesman Brian Fallon responded to the revelations without actually addressing any of these concerns, describing Gowdy's letter as "one more example of the partisan approach taken throughout his thoroughly discredited investigation."

Unfortunately for Clinton's campaign, the FBI is also conducting an investigation.